■动作电位通常沿着神经元的轴突直行,从轴突初始段(AIS)向突触前末端。在某些情况下,动作电位也向相反方向传播,抗屈体,在远端位置开始后。鉴于它们是在非典型部位开始的,我们将这些事件称为“异位动作电位”。“异位动作电位(EAP)最初是在包括癫痫发作和神经损伤在内的病理条件下观察到的。一些研究已经描述了在癫痫发作模型中发射EAP的规则尖峰(RS)锥体神经元。在非病理条件下,EAP被报道在少数神经元群体中,我们的研究小组发现,EAP可以在新皮质中大部分表达小清蛋白的中间神经元中诱导。然而,据我们所知,以前没有关于新皮层中最大的神经元群异位放电的报道,锥体神经元,在非病理条件下。
■我们利用全细胞膜片钳技术进行了体外记录。要引发EAP,我们用两种方法触发了直行的电位,逐步增加当前的步骤,或者以30、60或100Hz的短脉冲序列以3种不同的方式传递,刺激和静息期持续时间不同。
■我们发现,来自小鼠的大部分(72.7%)新皮质RS细胞在体外特定刺激后可以激发EAP,并且大多数RS细胞(56.1%)能够在宽范围的刺激条件下激发EAP。在我们能够引发EAP的37个RS神经元中,在第一次EAP出现前,平均约81.4s的时间内,平均产生863.8个直行动作电位.我们观察到一些细胞响应特定的刺激频率,而选择性较低,建议在细胞的子集进行频率调谐。
■我们的发现表明,锥体细胞可以在长时间尺度上整合信息,然后短暂进入起源于远端轴突的自我生成放电模式。RS细胞中EAP生成的令人惊讶的普遍性引发了关于异位尖峰在信息处理中的潜在作用的有趣问题。皮质振荡,和癫痫易感性。
UNASSIGNED: Action potentials usually travel orthodromically along a neuron\'s axon, from the axon initial segment (AIS) toward the presynaptic terminals. Under some circumstances action potentials also travel in the opposite direction, antidromically, after being initiated at a distal location. Given their initiation at an atypical site, we refer to these events as \"ectopic action potentials.\" Ectopic action potentials (EAPs) were initially observed in pathological conditions including seizures and nerve injury. Several studies have described regular-spiking (RS) pyramidal neurons firing EAPs in seizure models. Under nonpathological conditions, EAPs were reported in a few populations of neurons, and our group has found that EAPs can be induced in a large proportion of parvalbumin-expressing interneurons in the neocortex. Nevertheless, to our knowledge there have been no prior reports of ectopic firing in the largest population of neurons in the neocortex, pyramidal neurons, under nonpathological conditions.
UNASSIGNED: We performed in vitro recordings utilizing the whole-cell patch clamp technique. To elicit EAPs, we triggered orthodromic action potentialswith either long, progressively increasing current steps, or with trains of brief pulses at 30, 60, or 100 Hz delivered in 3 different ways, varying in stimulus and resting period duration.
UNASSIGNED: We found that a large proportion (72.7%) of neocortical RS cells from mice can fire EAPs after a specific stimulus in vitro, and that most RS cells (56.1%) are capable of firing EAPs across a broad range of stimulus conditions. Of the 37 RS neurons in which we were able to elicit EAPs, it took an average of 863.8 orthodromic action potentials delivered over the course of an average of ~81.4 s before the first EAP was seen. We observed that some cells responded to specific stimulus frequencies while less selective, suggesting frequency tuning in a subset of the cells.
UNASSIGNED: Our findings suggest that pyramidal cells can integrate information over long time-scales before briefly entering a mode of self-generated firing that originates in distal axons. The surprising ubiquity of EAP generation in RS cells raises interesting questions about the potential roles of ectopic spiking in information processing, cortical oscillations, and seizure susceptibility.